The present invention provides novel organic compounds and pharmaceutical compositions containing such compounds. These compounds may be useful in the treatment of cancer, particularly cancers in which agents that target the spliceosome and mutations therein are known to be useful.
In eukaryote organisms, newly synthesized messenger RNAs typically have multiple introns, which are excised to provide the mature mRNA. The spliceosome is a multisubunit complex that accomplishes this task. The spliceosome consists of five small nuclear RNAs (snRNAs; U1-6) in combination with a variety of proteins. Mutations in spliceosome genes have been found in various types of cancers.
For example, mutations in the splicing factor 3B subunit 1 (SF3B1) of the spliceosome exist in a number of cancers and comprise a target for anticancer agents. Such cancers include, but are not limited to, myelodysplastic syndrome (MDS), leukemia such as chronic lymphocytic leukemia (CLL), chronic myelomonocytic leukemia (CMML), and acute myeloid leukemia (AML), and solid tumors such as breast cancer and uveal melanoma.
Compounds isolated from the bacteria Streptomyces platensis (Sakai, Takashi; Sameshima, Tomohiro; Matsufuji, Motoko; Kawamura, Naoto; Dobashi, Kazuyuki; Mizui, Yoshiharu. Pladienolides, New Substances from Culture of Streptomyces platensis Mer-11107. I. Taxonomy, Fermentation, Isolation and Screening. The Journal of Antibiotics. 2004, Vol. 57, No. 3.), termed pladienolides and discovered while screening for inhibitors of the vascular endothelial growth factor (VEGF) promoter, inhibit expression of a reporter gene controlled by human VEGF promoter, which inhibition is known to be a useful mechanism of action for anticancer agents.
These compounds also inhibit proliferation of U251 human glioma cells in vitro. The most potent of these compounds, Pladienolide B, inhibits VEGF-promoted gene expression with an IC50 of 1.8 nM, and inhibits glioma cell proliferation with an IC50 of 3.5 nM. The structure of pladienolide B is known, (Sakai, Takashi; Sameshima, Tomohiro; Matsufuji, Motoko; Kawamura, Naoto; Dobashi, Kazuyuki; Mizui, Yoshiharu. Pladienolides, New Substances from Culture of Streptomyces platensis Mer-11107. II. Physico-chemical Properties and Structure Elucidation. The Journal of Antibiotics. Vol. 57, No. 3. (2004)) and pladienolide B is known to target the SF3b spliceosome to inhibit splicing and alter the pattern of gene expression (Kotake et al., “Splicing factor SF3b as a target of the antitumor natural product pladienolide”, Nature Chemical Biology 2007, 3, 570-575).
Certain pladienolide B compounds, as well as other pladienolide compounds, are likewise known, as disclosed the following patent applications: WO 2002/060890; WO 2004/011459; WO 2004/011661; WO 2004/050890; WO 2005/052152; WO 2006/009276; and WO 2008/126918. For example, a pladienolide compound, (8E,12E,14E)-7-((4-Cycloheptylpiperazin-1-yl)carbonyl)oxy-3,6,16,21-tetrahydroxy-6,10,12,16,20-pentamethyl-18,19-epoxytricosa-8,12,14-trien-11-olide, also known as E7107, is a semisynthetic derivative of the natural product pladienolide D, and the results of its Phase I study have been reported.
However, additional agents useful in the treatment of cancer, particularly cancers in which agents that target the spliceosome and mutations therein are known to be useful, are needed.